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Updated 12 April 2018 11:27am

Diphacinone – what is it?

Diphacinone is a first generation anticoagulant poison used by Greater Wellington Regional Council (GWRC) to control rats.

This poison was first introduced into New Zealand in the 1950s to control rodents.

Diphancinone bait is often known as Pestoff 50D.

It comes in small, hard, dyed green cylindrical cereal pellets which we place in bait stations in control operations.


Pestoff Rat Bait 50D diphacinone pellets


Important points to remember

  • The bait stations must be located out of reach of children, pets and stock
  • Warning signs must be erected at all main access points to public areas where Diphacinone bait stations are placed
  • Diphacinone baits are dyed green

Danger to humans

Diphacinone (Pestoff 50D) like any other poison, is dangerous if eaten. However it’s less toxic than other common poison baits. Humans need to eat very large amounts of the toxic bait for it to be fatal. There have been no accidental fatalities recorded in New Zealand.

Children should be kept away from all bait stations.


Pelifeed bait station filled with anti-coagulant bait

Pelifeed bait station filled with anti-coagulant bait


Danger to pets

Diphacinone (Pestoff 50D) is less hazardous than other common poisons but care is still necessary to prevent pets from being accidentally poisoned by eating toxic bait or carcasses. The risk of pets being poisoned from eating poisoned carcasses is very low.

If you see pets eating toxic bait, induce vomiting as soon as possible and take them to a vet.

A vet can administer Vitamin K1, which is an effective treatment, but it must be given in the early stages of poisoning.

Symptoms of poisoning

The symptoms are similar for both humans and other mammals. Nausea and vomiting may occur soon after ingestion. However, in some cases the effects from exposure to Diphacinone may be delayed for several days. Typical symptoms of poisoning include:

  • Bleeding gums
  • Increased tendency to bruising
  • Blood in urine and faeces
  • Excessive bleeding from minor cuts
  • Moving with difficulty
  • Shock
  • Coma


Do not rely on treatment. Prevention is the best method of protection from poisoning.

If poisoning is suspected, seek medical advice immediately or call the National Poison Centre 0800 764 766.

If bait has been swallowed, give a glass or two of water and induce vomiting by putting a finger down the throat. Repeat until the vomit is clear in appearance.

Safety precautions

  • Store bait in a safe place, away from foodstuffs, children and pets
  • Avoid contact with skin
  • Wear overalls and waterproof gloves when handling bait
  • Avoid contamination of any water supply with baits or empty containers
  • Do not eat, drink or smoke while using
  • Wash hands and exposed skin after applying bait

Effects on drinking water

Diphacinone is most unlikely to be found in water because bait is placed in bait stations and kept clear of streams and waterways.

Danger to livestock

Livestock exposed to Diphacinone (Pestoff 50D) should not be sent to slaughter or sold. A two month withholding period applies for livestock and milk production.

It is an offence under the Meat (Residues) Regulations Act to send animals for slaughter that contain chemical residues above prescribed limits. In the case of poisons any detectable residue is considered a violation.

If you decide to send contaminated livestock to the meatworks, you must contact the Ministry of Primary Industries veterinarian at the processing plant before transporting the animals.

If dairy cattle become exposed to Diphacinone, immediately notify the dairy supply company. If deaths occur in sheep or cattle, the entire flock or herd should be withheld for two months.

Please notify Greater Wellington Regional Council if you suspect livestock has been exposed to poison baits. Greater Wellington may have to notify the Medical Officer of Health.

Danger to feral game

Any residues are eliminated from the animals in about three weeks. Do not take game from the area for two months after treatment has ceased.

Toxicity to other animals


LD 50


Animal weight (kg)

Amount of bait to kill (gms)





Norway Rat















150000 (150kg)

Chart is based on Diphacinone LD50s – amount of toxic bait required to kill 50% of a population.